164 



Fishery Bulletin 105(2) 



used as the price. Round-trip travel cost ittc) is calcu- 

 lated as the following; 



ttc = ($0.33 X distance x 2) + ( [^^ffS'H^E^^ + ^rsf 



\ 40 



xlost _ income x w. 



(7) 



where distance = the one-way distance from the anglers 

 home zip code to the zip code, or lati- 

 tude/longitude, of the intercept site. 



This distance is multiplied by the Federal Travel Reg- 

 ulations reimbursement rate for private transportation 

 ($0.33) and includes both the fixed and variable costs 

 of operating an automobile. The variable lost_income is 

 a dummy that takes the value of 1.0 if the individual 

 did take time off work without pay to go fishing. If the 

 individual lost income, their wage rate («>) is multiplied 

 by the travel time plus the time on site (hrsf) and this 

 amount is added to the travel cost (40 miles per hour 

 is used as the average travel speed). Therefore, the 

 opportunity cost of onsite time and travel time is only 

 included if an individual took time off work to par- 

 ticipate in fishing on a given day. If the individual is 

 not losing income for the trip, his travel cost is simply 

 round-trip distance multiplied by the fixed and vari- 

 able costs of operating an automobile. As is typical for 

 these MRFSS data sets, very few anglers (3.34%) report 

 having foregone income to take the trip. To account for 

 the opportunity cost of time for those anglers not los- 

 ing income, travel time is used as a measure of time 

 cost for those individuals. In order not to double count 

 those that lost income taking a trip, the expression for 

 travel time itt) is 



tt = 



( (distance X 2) 





40 



)- 



lost _ income) . 



(8) 



Keeping only those anglers that have targeted or caught 

 striped bass from the boat mode on a single day trip 

 leaves 3630 usable observations. 



With an aggregation strategy in place and the vari- 

 ables defined, the estimation of the conditional logit 

 model follows. As a reminder, the choice of whether or 

 not to take a fishing trip, which mode to fish in, and 

 what species to pursue are made outside of this model. 

 The angler then chooses the site that maximizes in- 

 direct utility from his or her set of substitutes. Every 

 model carries a set of implicit assumptions. Angler 

 behavior within this model is defined on a trip-by-trip 

 basis and the angler is not allowed to modify the num- 

 ber of trips taken each season. Therefore, each choice 

 is independent of the next, and unobservable utility, 

 f^, is independent of any other trips. Additionally, the 

 MRFSS intercept survey is assumed to approximate a 

 random sample of trips. The author acknowledges these 

 contentions with choice-based sampling in the MRFSS 

 data, and this is an area of research that this author 

 and NMFS scientists continue to explore. 



Variables in the deterministic portion of indirect util- 

 ity include travel cost ittc), travel time itt), log of the 

 number of MRFSS intercept sites aggregated into the 

 county site used in the model (m), and historic KRATE 

 per trip for striped bass at site 7 (q ). Indirect utility is 



I5^ttc,j + p^q, + p„tt,, + p,„ ln( m^ ) + E^. 



(9) 



With this expression for indirect utility, the probability 

 that angler i selects site 7 is 



P.ij)-- 





(10) 



and the expression for the change in compensating varia- 

 tion for a change in the historic catch and keep rate, 

 after assuming a constant marginal utility of income, 

 is the following: 







(11) 



where q° = the historic KRATE; and 



q^ = the KRATE after the environmental or policy 

 change. 



Table 1 provides descriptive statistics for all the vari- 

 ables to be used in the analysis and some angler-specific 

 attributes in order to give the reader some background 

 on these anglers. Throughout the range of this data col- 

 lection, the bag limit for striped bass is two fish per day. 

 On average, anglers catch far less than the limit. In 

 fact, the base catch rate for anglers targeting or catch- 

 ing striped bass from the boat mode is less than one 

 fish per trip. What is readily apparent is that there are 

 some irrational anglers in this group, at least concern- 

 ing travel time. The maximum travel time translates 

 into a 798 mile one-way travel distance, which does not 

 seem feasible for a one-day trip. Even after eliminating 

 those anglers that admit to taking an "overnight" trip, 

 there are obviously anglers that are away from home 

 longer than 24 hours. One explanation is that these 

 anglers live in the local area seasonally and have given 

 the zip code of their permanent address, which is used 

 to calculate travel distance. Another explanation arising 

 from the author's experience in the field is that some of 

 these anglers drive incredibly long distances and fish 

 for 24 or more hours. They do not consider their trip 

 to be an overnight trip because they are not staying 

 in a hotel even though their round trip travel distance 

 indicates that they were away from home for more than 

 24 hours. There were only 3 individuals in the data set 

 with one-way travel distances greater than 500 miles 

 and the results were not sensitive to leaving these out- 

 liers in the model. As a result they remain in the data 

 set. Other statistics of note include the variable that 



